The present invention relates to signage. More particularly, the present invention relates to perforated film constructions for use in backlit signs that provide one appearance under light ambient light conditions (such as daytime lighting), and another appearance when backlit and under dark ambient lighting conditions (such as nighttime).
Illuminated signs, sometimes referred to as light boxes, are often used to enhance the presentation of images and/or text. Examples of illuminated signs can be found in, e.g., airports, mass-transit stations, shopping malls and other public places. The signs typically include an enclosure having an illuminated face over which a graphic (including images and/or text) is located. The illumination is typically provided by lamps located behind the sign face and within the enclosure. The images and/or text in the graphic typically include transparent or translucent portions to enhance their visibility when placed over the illuminated face.
Common terminology used in connection with such signs refers to surfaces adapted to face a viewer as xe2x80x9cfirst surfacesxe2x80x9d and surfaces adapted to face the interior of the sign box (i.e., away from the viewer) as xe2x80x9csecond surfaces.xe2x80x9d That terminology will be used below.
Today there are four commonly used methods for making color by day and white by night back lit signage. The first method (which will only work to provide black and darker shades of gray or blue by day and white by night) uses a translucent black, gray or blue sign face. During the day (or other conditions where the light outside the sign box is light used for viewing the sign face) the color seen by the viewer is the reflected color off of the first surface of the sign face. The color seen by the viewer at night (or other conditions where the light inside the sign box is used for viewing the sign face) is the transmitted color. With this construction, the color of the sign face is washed out and, to the eye, appears white under nighttime viewing.
The second and third methods use block-out films. Block-out film is a two-layer construction where one layer is white and the second layer is a black, with the two layers combining to provide an opaque construction. Adhesive is applied to the dual film construction on the black side of the film (which serves as its second surface).
The second method takes block-out film and laminates a colored film to the white side (which serves as its first surface). This laminated construction is cut (often on a flat bed cutter) into thin lines of film. The film is cut in such a manner as to have alternating 9.5 mm (xe2x85x9c-inch) strips of film separated by 3.2 mm (xe2x85x9 inch) open spaces across the sign face. The black sides of the strips are adhered to a translucent substrate with the colored surface facing the viewer to provide reflected color by day. At night, when the sign is illuminated from behind, light passing through the open spaces provides a white appearance. In some instances a color may be provided during backlighting by the use of colored bulbs, colored filters, colored diffusers, etc., such that light transmitted through the open spaces between the film strips has a color.
The third method of making a color by day white by night film is to punch block-out film with small holes and then screen print the white side to obtain a desired color in daytime viewing (under light reflecting from the first surface of the sign face). Generally, the area occupied by the holes in the punched film is 40% to 50%. The black surface of the block-out film is adhered to a translucent substrate with the white or printed surface facing the viewer to provide reflected color by day. At night, when the sign is illuminated from behind, light passing through the holes provides a white appearance. In some instances, a color may be provided during backlighting by the use of colored bulbs, colored filters, colored diffusers, etc., such that light transmitted through the holes has a color.
The fourth method of making color by day and white by night backlit signage uses paint. This involves painting a translucent face with black paint, followed by painting a second layer of color over the black paint. This dual coated face is then routed to form lines through the paint exposing the translucent face as desired. When backlit, the areas in which the paint has been removed transmit light to a viewer. During daylight, the sign takes on the appearance of the color or colors applied to the black paint.
All of these constructions have a major disadvantagexe2x80x94an absorptive layer (typically black or a darker shades of gray or blue) oriented towards the light source. The absorptive layer absorbs the light from the light source, thereby reducing the efficiency of the sign box. Another disadvantage of first method is that the dark gray or black rigid plastic is very expensive and this method is effective with only a few colors. Other disadvantages of the second and fourth methods (above) are their cost and labor intensive nature. Yet another disadvantage of the third method is that the large percent open area (40%-50%) often causes the color in the sign face to appear washed-out in the daytime and requires printing to obtain a desired color.
The present invention provides film constructions and signs including the constructions that are capable of having one appearance under light ambient lighting conditions, and another appearance when backlit under dark ambient lighting conditions. The construction is generally planar and includes perforations that are separated by an opaque land area. The second surface of the film construction in the land area (i.e., the surface that is adapted to face the interior of the sign) reflects, e.g., at least about 50% of normal light incident thereon.
In some instances, it may be preferred to provide larger or more numerous perforations that occupy, e.g., up to about 35% of the major surfaces of the construction. Film constructions with increased open area may provide improved brightness when backlit at night or in areas with lower levels of ambient light.
One advantage of the present invention is that backlit signs manufactured using the perforated constructions of the present invention can provide significant increases in brightness. In some instances, brightness of the signs when backlit can be as high as 120%, to more than 200%, as compared to signs using conventional films.
In one aspect, the present invention provides a generally planar film construction including a front surface and a back surface. A plurality of perforations are distributed over the construction, wherein each of the perforations transmits light through the front and back surfaces of the construction. Opaque land area separates the plurality of perforations and layer of adhesive is provided proximate the back surface of the construction. The perforations occupy about 10% to about 30% of the front and back surfaces of the construction, and at least about 50% of normal incident light directed at the land area of the back surface of the construction is reflected.
In another aspect, the present invention provides a sign face capable of having one appearance under light ambient lighting conditions, and another appearance when back lit and under dark ambient lighting conditions. The sign face includes a substrate having a first surface and a second surface. A film construction is attached to the first surface of the substrate, the construction including a front surface and a back surface, the back surface facing the first surface of the substrate. A plurality of perforations are distributed over the construction, wherein each of the perforations transmits light through the front and back surfaces of the construction. Opaque land area separates the plurality of perforations. The perforations occupy about 10% to about 30% of the front and back surfaces of the construction, and at least about 50% of normal incident light directed at the land area of the back surface of the construction is reflected.
In another aspect, the present invention provides a backlit sign including the sign face described above mounted on an enclosure.
These and other features and advantages of the invention are described below in connection with illustrative embodiments of the invention.
For purposes of the present invention, xe2x80x9cfilmxe2x80x9d means a sheet-like article having opposing major surfaces, capable of being handled and stored as a separate article.
For purposes of the present invention, xe2x80x9cgenerally planarxe2x80x9d means a construction having a relatively thin profile, with opposing major surfaces. Perforations are placed in the construction through the thinner dimension, so that light will pass through the construction and be visible when viewing the construction perpendicular to the major surfaces.
For purposes of the present invention, xe2x80x9clightxe2x80x9d means, unless otherwise specified, electromagnetic radiation in wavelengths that are typically visible to the unaided human eye.
For purposes of the present invention, xe2x80x9cnormal incident lightxe2x80x9d or xe2x80x9cnormal light incident thereonxe2x80x9d mean light approaching a surface at a 90xc2x0 angle to that surface.
For purposes of the present invention, xe2x80x9copaquexe2x80x9d means transmission of less than about 0.01% of light within the spectrum of interest. For example, when used in connection with a backlit sign, an opaque construction will transmit less than about 0.01% of light emitted by the light sources located within the sign.
Reflectivity and transmission of the films and other materials discussed herein can be determined using a SPECTRAFLASH 500, available from Datacolor International, Lawerenceville, N.J. using the standard techniques for operating the device. The average reflectance/transmission values are over the wavelength range of 500-600 nanometers.